In client-server applications, a user interacts directly with a client computer system to use an application program executing on a server computer system, which is often physically remote from the client computer system. In some client-server applications, data can be created in a database managed by the application, and retrieved, manipulated, and displayed based upon a combination of user commands and business rules incorporated in the application. For example, a typical application may be used by users to store, retrieve, and manipulate information about the users' relationships with customers.
Original client-server applications provided little functionality at the client computer system beyond displaying data, allowing the user to enter data and instructions, and allowing the user to submit entered data or instructions to the server. For example, the user may enter text into each field of a displayed 15-field form, then select a submit button to submit all of the entered text to the application on the server.
Client-server applications having such “low-interactivity” user interfaces have the advantage that they impose modest requirements on client hardware, which can typically be satisfied by dumb terminals or microcomputer systems running very simple client programs, such as terminal emulators or basic web browsers. Additionally, because only small quantities of data and instructions are passed between client and server by low-interactivity user interfaces, inexpensive and ubiquitous low-speed connections between client and server are typically adequate to support low-interactivity user interfaces.
Low-interactivity user interfaces have significant disadvantages, however. Because the user of a low-interactivity user interface can typically only enter data into all of the fields of a displayed form, then submit the contents of the entire form, the user is unable to obtain any feedback from the application during the time that the user is filling out individual fields of the form. For example, if the user enters an invalid value into the first field of a 15-field form, the user will not discover the error until after the user has filled out all 15 fields and submitted their contents. Further, once the user has entered a valid value into a field of a form, the application has no mechanism to modify the set of fields displayed in the form, or suggest a value for another field in the form, based upon entry of the value.
Some disadvantages of low-interactivity user interfaces are overcome by conventional high-interactivity user interfaces for client-server applications. Typical conventional high-interactivity user interfaces are constructed by defining web pages in Dynamic Hypertext Markup Language (DHTML), which are delivered to a web browser on the client computer system together with JavaScript code. The JavaScript code for responds to various types of user input by updating the web page by modifying its DHTML definition. Such modification may be done based on logic in the JavaScript code, or based on logic in the server code for the application in response to a request transmitted by the JavaScript code. Such conventional high-interactivity user interfaces are typically able to provide a higher level of interactivity, by processing user input events such as individual keystrokes and mouse clicks, and providing feedback directly in response to these finer-grained events.
Conventional high-interactivity user interfaces have their own disadvantages, however.
In most web browsers, DHTML is slow to update, no matter what mechanism is used to update it. Additionally, because JavaScript is an interpreted language, the JavaScript code used in typical conventional high-interactivity user interfaces executes slowly, further degrading the performance, and therefore the apparent responsiveness, of typical conventional high-interactivity user interface implementations.
Accordingly, a high-interactivity user interface for client-server applications that overcomes the above-discussed disadvantages of typical low-interactivity user interfaces and conventional high-interactivity user interfaces would have significant utility.